Motors sitting for 4 years.
Motors sitting for 4 years.
(OP)
I'm currently working at a site that was inactive for the last 4 years. In their great wisdom, the last contractor to leave site left all the electric motors out in a shed out back.
The site owner wants to test the motors intergrity before coupling. His question to me was, "Is there any rule of thumb on this?" and goes on to explain that he wants to know if there are any HP ranges that should be tested and for how long. Such as 50-100 hp motors need to be tested for 2 hours.
Motors are all 3-phase, some are 480, some are 4160V.
Does anyone have any expereince with this, so at least I can go in the right direction?
The warrentys on these motors have long since expired and they want to do all the work on site. We have motors from 1-300 HP, the site is a power plant.
Thanks in advance to anyone who can help out!!!
The site owner wants to test the motors intergrity before coupling. His question to me was, "Is there any rule of thumb on this?" and goes on to explain that he wants to know if there are any HP ranges that should be tested and for how long. Such as 50-100 hp motors need to be tested for 2 hours.
Motors are all 3-phase, some are 480, some are 4160V.
Does anyone have any expereince with this, so at least I can go in the right direction?
The warrentys on these motors have long since expired and they want to do all the work on site. We have motors from 1-300 HP, the site is a power plant.
Thanks in advance to anyone who can help out!!!





RE: Motors sitting for 4 years.
Then megger them or do Baker test.
The bearings may have false brinelling, but probably not in this size range. Grease doesn't age much at low temperature. And four years is not such a long time after all. Turn the rotor by hand and see if all seems to be OK, smooth turning, no binding.
Start them on reduced voltage (so you do not have to screw them down) and listen for noise from the bearings. A vibration analyzer may be used but does often produce too high values if motors are run standing on the floor.
Cleaning and visual inspection is of course also something that shouldn't be forgotten.
Gunnar Englund
www.gke.org
RE: Motors sitting for 4 years.
One thing I would clarify is that any surge testing (Baker test equipment) should not be done until the megger and PI indicate drying is complete. Surge test on damp winding can damage the winding (similar to hi-pot testing in that respect).
=====================================
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RE: Motors sitting for 4 years.
If grease lubricated bearing, you might consider disassembling the motor to repack the grease (unfortunately usually dictates replacing bearings as well).
If oil-lubricated bearings, you might sample, flush, sample at some point (of course motor has to be drained for movement), and preferably inspect bearings if easily accessible.
Depending on the plant situation, in some cases a shop unloaded run would be a good idea prior to installing in the plant. In other cases when there is anticipated enough time to address any problems after plant uncoupled run, it would be a waste of time to perform shop uncoupled run.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Motors sitting for 4 years.
RE: Motors sitting for 4 years.
Dry and megger, or megger, dry, and megger.
Don't forget to check for nests of small animals before starting.
respectfully
RE: Motors sitting for 4 years.
http://www.reliance.com/prodserv/motgen/h7000.htm
Chuck
RE: Motors sitting for 4 years.
RE: Motors sitting for 4 years.
I disagree with most of the opinions above. Four years inactive is a lot of time for electric motors. One of the main problems is moisture condensation which will produce deep contamination into the insulation and will develop bearings corrosion.
Make a detailed disassembled test and inspection to define the required recondition for each motor. At least bearings must be changed and winding reconditioned.
The other option is; expensive random premature failures out of control.
RE: Motors sitting for 4 years.
RE: Motors sitting for 4 years.
RE: Motors sitting for 4 years.
RE: Motors sitting for 4 years.
Hi Riggspsk,
Just as above, it is better to make it sequential.
I've been in field services, and i did this manner:
1. Visual Inspection
2. Insulation resistance test
3. P.I Test
4. Surge Comp. Test
5. Check Bearing
6. Check Grease/Lube oil
7. No load test
While running at no - load add small amount of grease like
Calcium 12-hydroxy Grease where evidently have almost comptible to all grease type except Polyurea.
8. Load test
9. Condition monitoring
9.1. Temp. stabilize at least 1 hour
9.2. Vibration
9.3. Load currents
Any failure of subsequent test or inspection is subject to rectification or repair at your own discretion with an aid of published standard procedure. Else, suggestions posted as above would greatly help you out.